A taxonomic, biogeographical and ecological overview of invasive woody plants

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Abstract

Invasive plants are considered to be a major threat to the earth's biodiversity, but have not been sufficiently investigated. To address this problem a relational database on invasive woody plants has been set up. It is based on 2045 bibliographical references and contains records on 653 species representing 110 families. The families with the largest number of invasive species are: Rosaceae, Mimosaceae, Papilionaceae and Pinaceae. Out of 1060 recorded invasive events an equal number are reported from continents and oceanic islands. The highest number of invasive woody species are recorded from Europe, followed by the Pacific islands, North America, New Zealand, Australia, Indian Ocean islands and southern Africa. Included in these regions are areas which have fewer highly invasive species, e.g. islands on continental shelves, such as the British Isles. Although most invasions occur in disturbed habitats, most natural communities are susceptible to woody plant invasions. Data on species attributes are only available for a minority of species but indicate that invasive woody plant species may be either insect or wind-pollinated, have a wide array of fruit types, fruit and seed sizes, number of seeds per fruit and dispersal agents. The relative frequency of several attributes varies with the degree of invasiveness. Thus it is not yet possible to determine which set of attributes favours invasiveness and therefore it is difficult to make predictions.